The temperate oak forest of the Magdalena river basin, located in Mexico City, is often under anthropogenic disturbances which has facilitated the introduction of alien species. One of these species is Hedera helix that due to its fast growth and propagation is invading some areas of the forest, reaching high densities and cover values. The aims of this study were to asses and compares, during a year, the changes on plant structure and composition of invaded vs non-invaded sites as well as the natural regeneration in sites subjected to a manual removal of the introduced species. We established twenty 3 x 3m plots, five on an invaded site, five on a non-invaded site and five plots on each site where the understory plant cover was removed. All these plots were monitored every 2 months for quantify and measure all individuals and cover values of each species present and later we estimate the species richness, diversity index and the relative importance value for each species. We also collected soil samples at two different seasons to compare the chemical composition of soil between sites.
Results/Conclusions
The results showed that the individual densities of all species were lower in the invaded sites in almost all the months, due to the reduction of the available space by H. helix. Regarding the species richness and diversity, there were no statistically differences between treatments, however, the species accumulation curve through time was lower in the invaded sites; this could be because several species established before the invasion process and can coexist with H. helix, but there was a low germination of new species in these sites. A multivariate clustering showed that the plant composition in both removed and control sites were similar between them and more similar with the non-invaded sites. It means that the presence of H. helix originates a different plant composition, and after a mechanical removal control the early regeneration seems more like the non-invaded sites. In both seasons, the chemical composition of soil was similar between treatments, except for the potassium (K) which was higher in the invaded sites.